Abstract: As the main stream for urban construction, migrant workers play an important role in the process of realizing a well-off society. But their medical security situation is worrisome. The demands for medical and health security have become a problem yet to be solved. As a system dispersing and transferring of all social members' revenue risks generated by disease, medical security plays an important role in demanding of health and medical-care. As an extended need of people's health need, seeking medical treatment is subject to restriction of various factors. Based on the health need theory,the present empirical study explores the correlation between medical security and seeking medical treatment behavior. The results are as follows: the situation of migrant workers' possession of health insurance varies,medical security has notable effect on seeking medical treatment behavior,and current medical insurance policy still constraints the policy of migrant workers.